Lastpharaoh

what Wikipedia says is best I read ever :

Dominance and submission (also called D&s, Ds, and D/s)^[1] is a set of behaviors, customs and rituals involving the giving by one individual to another individual of control over them in an erotic episode or as a lifestyle.

Physical contact is not a necessity, and it can even be conducted anonymously over the telephone, email or other messaging systems. In other cases, it can be intensely physical, sometimes traversing into sadomasochism. In D/s, both parties take pleasure or erotic enjoyment from either dominating or being dominated. Those who take the superior position are called dominants, doms (male) or dommes (female), while those who take the subordinate position are called submissives or subs (male or female). A switch is an individual who plays in either role. Two switches together may negotiate and exchange roles several times in a session. "Dominatrix" is a term usually reserved for a female professional dominant who dominates others for pay.